The invention relates to an electrical layer capacitor which is composed of a solidified stack of synthetic layers and metal coatings alternating with one another. The metal coatings are applied in regenerably thin manner to the synthetic layers. The stack has metal layers at opposite lateral faces which electrically connect the metal coatings of a same polarization to one another and in turn can serve for connecting the electrical capacitor to external power supply elements.
Electrical layer capacitors of this type and methods for the manufacture thereof are adequately disclosed in the corresponding technical literature.
Thus, German Pat. No. 492 621, incorporated herein by reference, discloses layer capacitors which have arisen by superimposed stacking of dielectric layers provided with metal coatings as electrodes, and by parting the stack in a longitudinal direction and at right angles thereto. Another form of layer capacitor has arisen by folding correspondingly metalized tapes. Finally, electrical layer capacitors of this type have arisen by winding tapes having a corresponding arrangement of the metal coatings onto a drum, and by dividing this winding at right angles to the longitudinal axis of the drum and then in a radial direction. The insulation both at the lateral faces, at which coatings of the same polarization are connected to one another by means of additional metal layers, as well as at the parting surface, at which all metal coatings are present, occurs by means of an appropriate selection of metal-free strips which are generated in the metallization of the tapes to be stacked or wound.
Given the electrical layer capacitor disclosed by German Pat. No. 975 263, incorporated herein by reference, the insulation surfaces between the different coatings at the parting surface are achieved, among other things, in that an adequately high voltage is applied to the finished capacitor so that the coatings burn off.
German Pat. No. 1 764 540, incorporated herein by reference, discloses a method for the manufacture of electrical layer capacitors which has proven itself in practice through wide use for many years and is comprised therein that metallized tapes corresponding to the width of the desired capacitor are wound onto a large diameter wheel. A mother capacitor ring thus results after a number of windings have been completed corresponding to the capacitance of the desired capacitor. A parting ply is then wound into at least one winding, and the next mother capacitor is then wound thereon. The next parting ply is then added and so forth until an initial capacitor composed of a plurality of mother capacitor rings has arisen. While still on the wheel, this initial capacitor is provided with metal layers at both end faces by means of the known schoopage method wherein small drops of molten metal are sprayed onto the surface to be metallized. They are sprayed, for example, by means of compressed air (see for example, U.S. Pat. Nos. 1,128,058 or 3,256,472, both incorporated herein by reference). After appropriate consolidation steps, the initial capacitor is divided into the individual mother capacitor rings. Obtained from these mother capacitor rings by cutting is a capacitor which may still have to be provided with power leads, be shock regenerated for curing defects, and finally is finished as an electrical layer capacitor.
The product of this method is described in detail in the periodical "Radio Mentor", 1972, No. 1, pp. 022 and 023, incorporated herein by reference.
European Pat. No. Al-0 011 033, incorporated herein by reference, and having a priority of October, 1978 also discloses a manufacturing method for such an electrical layer capacitor in detail. It is also disclosed therein that the edges of the tapes need not be cut straight. Rather, corresponding configurations can be selected as was already similarly presented in German Pat. No. 24 16 566, incorporated herein by reference.
This edge formation serves the purpose of improving the electrical and mechanical connection of the metal layers to be applied to the lateral faces by the schoopage method, namely their connection to the metal coatings on the dielectric films. The simplest way of effecting this electrical connection is achieved in that two metallized tapes which are respectively cut straight at both sides are wound offset relative to one another by a certain amount, so that a free space into which the metal of the contacting metal layer can penetrate respectively remains above the metallization extending up to the edge.
In the manufacture of layer capacitors according to the above-described wheel winding method, this method is applicable because the exact guidance of the layers, which is absolutely necessary in this method, is thereby guaranteed.
German AS No. 22 27 751 (corresponding to U.S. Pat. No. 3,855,507, incorporated herein by reference), likewise discloses a layer capacitor wherein tapes provided with metal coatings at both sides are wound offset relative to one another on a large diameter wheel, whereby the opposite film coatings for a dielectrically effective plastic layer result from one tape each.
In a capacitor whose dielectric is generated by glow polymerization of the monomer of a plastic from the vapor phase, for which purpose a metal coating is first vapor-deposited onto a plastic carrier film, the dielectric is generated thereon and a further metal coating is in turn applied thereto as a cooperating electrode (see German Pat. No. 23 02 174 and German Pat. No. 29 00 772, both incorporated herein by reference). Here, a merely lateral offset of layers cut straight does not guarantee an adequate contacting of the respective coatings of the same polarity.